content: /*
   * Copyright 2017 David Karnok
   *
   * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in
   * compliance with the License. You may obtain a copy of the License at
   *
   * http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software distributed under the License is
   * distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See
   * the License for the specific language governing permissions and limitations under the License.
   */
  
  package hu.akarnokd.reactive4javaflow.impl.operators;
  
  import hu.akarnokd.reactive4javaflow.*;
  import hu.akarnokd.reactive4javaflow.impl.EmptySubscription;
  
  import java.util.concurrent.Flow;
  import java.util.concurrent.atomic.AtomicLong;
  
  /**
   * Limits both the total request amount and items received from the upstream.
   *
   * @param <T> the source and output value type
   * @since 0.1.4
   */
  public final class FolyamLimit<T> extends Folyam<T> {
  
      final Folyam<T> source;
  
      final long n;
  
      public FolyamLimit(Folyam<T> source, long n) {
          this.source = source;
          this.n = n;
      }
  
      @Override
      protected void subscribeActual(FolyamSubscriber<? super T> s) {
          source.subscribe(new LimitSubscriber<>(s, n));
      }
  
      static final class LimitSubscriber<T>
      extends AtomicLong
      implements FolyamSubscriber<T>, Flow.Subscription {
  
          private static final long serialVersionUID = 2288246011222124525L;
  
          final FolyamSubscriber<? super T> actual;
  
          long remaining;
  
          Flow.Subscription upstream;
  
          LimitSubscriber(FolyamSubscriber<? super T> actual, long remaining) {
              this.actual = actual;
              this.remaining = remaining;
              lazySet(remaining);
          }
  
          @Override
          public void onSubscribe(Flow.Subscription s) {
              if (remaining == 0L) {
                  s.cancel();
                  EmptySubscription.complete(actual);
              } else {
                  this.upstream = s;
                  actual.onSubscribe(this);
              }
          }
  
          @Override
          public void onNext(T t) {
              long r = remaining;
              if (r > 0L) {
                  remaining = --r;
                  actual.onNext(t);
                  if (r == 0L) {
                      upstream.cancel();
                      actual.onComplete();
                  }
              }
          }
  
          @Override
          public void onError(Throwable t) {
              if (remaining > 0L) {
                  remaining = 0L;
                  actual.onError(t);
              } else {
                  FolyamPlugins.onError(t);
              }
          }
  
          @Override
          public void onComplete() {
              if (remaining > 0L) {
                  remaining = 0L;
                  actual.onComplete();
              }
          }
  
          @Override
          public void request(long n) {
              for (;;) {
                  long r = get();
                  if (r == 0L) {
                      break;
                  }
                  long toRequest;
                  if (r <= n) {
                      toRequest = r;
                  } else {
                      toRequest = n;
                  }
                  long u = r - toRequest;
                  if (compareAndSet(r, u)) {
                      upstream.request(toRequest);
                      break;
                  }
              }
          }
  
          @Override
          public void cancel() {
              upstream.cancel();
          }
  
      }
  }